Injector with adjustable dosing

ABSTRACT

An injector for injecting a medicament in a patient. The injector includes a container comprising a fluid chamber containing a first volume of a medicament, and an injection conduit associated with the fluid chamber for defining a fluid pathway therefrom to inject the medicament from the fluid chamber through the injection conduit to an injection location. The injector also includes a firing mechanism associated with the fluid chamber for expelling the medicament from the fluid chamber through the injection conduit, and a volume-control mechanism operable to control a fraction of the first volume of medicament that is injected when the firing mechanism is actuated to inject the medicament.

This application is a 371 filing of International Patent ApplicationPCT/US2007/068010 filed May 2, 2007, which claims the benefit ofapplication of application No. 60/796,942 filed May 3, 2006.

FIELD OF THE INVENTION

The present invention relates to an injector, and more particularly toan injector with adjustable-dosing.

BACKGROUND OF THE PRESENT INVENTION

Injection devices for injection of medicaments into a patient aregenerally known. Such devices include, for example, traditionalhypodermic needle syringes that contain a stock of medicament therein.Upon insertion of the needle wider the patient's skin at an injectionlocation, the medicament is forced out of the syringe and through theneedle by depression of a plunger mechanism.

Injection devices also include needle-free injectors, some of which aredescribed in U.S. Pat. Nos. 5,599,302; 5,062,830; and 4,790,824; andneedle-assisted injectors, such as those described in U.S. PatentPublication No. 2005/0033234. These jet injectors administer medicamentsas a fine, high velocity jet delivered under sufficient pressure toenable the jet to pass through the skin, or for improved dispersion ofthe injected medicament. Self-injectors or autoinjectors like the onesdisclosed in U.S. Pat. Nos. 4,553,962 and 4,378,015, and PCTPublications WO 95/29720 and WO 97/14455 are constructed to injectmedicament at a rate and in a manner similar to hand-operated hypodermicsyringes.

These injectors often are made for a single use, or alternatively to berefilled after each injection. Some refillable injectors can he refilledwith a desired dosage to be injected. Upon injection, the entire loadeddosage is injected.

An injector is needed that can deliver a medicament into a patient in anadjustable dose that is equal to or less than the full amount containedin the injector.

SUMMARY OF THE INVENTION

The invention is related to an injector. A preferred embodiment of theinjector includes a container comprising a fluid chamber containing afirst volume of a medicament, and an injection conduit associated withthe fluid chamber for defining a fluid pathway therefrom to inject themedicament from the fluid chamber through the injection conduit to aninjection location. The injector also includes a firing mechanismassociated with the fluid chamber for expelling the medicament from thefluid chamber through the injection conduit, and a volume-controlmechanism operable to control a fraction of the first volume ofmedicament that is injected when the firing mechanism is actuated toinject the medicament.

Preferably, the volume-control mechanism is used to select a secondvolume, which is a portion or fraction of the first volume. Thevolume-control mechanism preferably includes a threaded ram that isbiased by an energy source against a plunger and configured for rotatingabout a longitudinal axis of the injector. The volume-control mechanismalso preferably includes a stopping member in threaded association withthe ram and including at least one lateral member disposed within atrack that extends longitudinally along a portion of the housing of theinjector and is slidable therein. Preferably, the stopping memberincludes a pair of opposing lateral members, each disposed in separateopposing tracks. The lateral member prevents rotation of the stoppingmember about the longitudinal axis with the ram when the ram is rotatedthereabout. The stopping member is configured for limiting movement ofthe ram along the longitudinal axis, the position of the stopping memberbeing adjustable along the longitudinal axis with respect to the ram.The volume-control mechanism also includes a cap associated, andpreferably removeably engageable, with the ram and configured forrotating the ram about the longitudinal axis to select an injectionvolume such that when the ram is rotated, the position of the stoppingmember is adjusted along the longitudinal axis with respect to the rain.Upon actuation of the energy source, which is preferably a spring,biasing of the ram against the plunger is preferably limited when thelateral member abuts the distal end of the track.

In one embodiment, the housing includes a transparent window adjacentthe length of the track such that the longitudinal position of thestopping member within the injector is visible through the window.Preferably, the transparent window includes indicia corresponding to theposition of the stopping member and the selected injection volume.

Preferably, the injector also includes a bearing member, such as anannular bushing or other bearing, disposed between the energy source andthe ram, and configured for preventing or substantially reducingfriction therebetween when the ram is rotated. The injector ispreferably configured for single-use injection of medicament therefrom.Alternatively, the injector is configured for multiple injections ofmedicament therefrom.

In the preferred embodiment, the container is a prefilled syringe, andfurther includes an injection-assisting needle disposed in fluidcommunication with the fluid chamber, the needle having an injecting tipconfigured for piercing the patient's skin at the injection location.The housing houses the prefilled syringe and is configured for allowinginsertion of the needle at the injection location to an insertion pointthat is at a penetration depth below the patient's skin. The injectorpreferably includes a syringe support supportively mounting theprefilled syringe to the housing. In other embodiments, the container isa needle-free cartridge, or a cartridge comprising aninjection-assisting needle associated therewith.

In the preferred embodiment, the housing includes a retractable guardthat is movable between a protecting position, in which the injectionconduit is disposed within the guard, and an injecting position, inwhich the tip of the injection conduit is exposed for injection of themedicament at the injection location. A trigger mechanism is preferablyoperably associated with the energy source for actuation of the energysource to inject the medicament. Preferably, the trigger mechanism isconfigured for actuation of the energy source after the retractableguard is retracted from the protecting position. The retractable guardis preferably operably associated with the trigger mechanism to causethe trigger mechanism to activate the energy source when the guard isretracted to the injecting position.

The present invention thus provides an injector that enables a user tocontrol or adjust the dose of medicament that is intended to bedelivered to the patient.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a preferred embodiment of aninjector constructed according to the present invention, showing theinjector prior to injection;

FIG. 2 is a cross-sectional view thereof, taken from a viewingperspective that is rotated 90° about the longitudinal axis of theinjector front the perspective of FIG. 1; and

FIG. 3 is a perspective view of another embodiment of an injector.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a preferred embodiment of an injector 10 has anouter housing 12, defined between a proximal end 6 and a distal end 8,and configured for allowing a user, typically the patient him orherself, to handle the injector 10 and position the injector near oradjacent an injection location. The outer housing 12 preferably housesmost of the components of the injector 10. The injector 10 also includesa cover member 14 configured to associate with the outer housing 12 andcover the distal end of the injector 10 prior to use. A containersupport member 16 is housed within and mourned with the housing 12. Thecontainer support member 16 is configured to hold and position acontainer 18 within the injector 10. The container 18 can be, forexample, a cartridge, syringe, or any other suitable container forholding medicament therein. In the preferred embodiment shown in FIG. 1,the container is a prefilled syringe 18. Alternatively, instead of aprefilled syringe attached to a needle, the syringe can have a separateneedle that is associated and brought into fluid communication with themedicament container prior to or upon firing of the injector. In thepreferred embodiment, the container support member 16 is substantiallyfixed to the outer housing 12, such as by snaps, an adhesive, a weld, oranother known attachment. The container 18 has a container portion 20that defines in its interior a fluid chamber 22, which is preferablyprefilled with medicament to be injected. In another embodiment,however, this chamber can initially be provided empty.

At the distal end of the container 18 is an injection-assisting needle24, which is in fluid communication with an injection port 25 of thefluid chamber 22. Needle 24 has an injecting tip 26 configured as knownin the art to penetrate the tissue of a patient, preferably the skin, atthe injection location. A needle bore extends through the needle 24, asknown in the art. The bore is in fluid communication with the injectionport 25 and the medicament in the fluid chamber 22, and is open at theneedle tip 26 to inject the medicament.

In needle-free injector embodiments, the container does not include aneedle and the injection port of the fluid chamber preferably defines afluid pathway in fluid communication with the fluid chamber forinjecting medicament as a jet from the chamber through the port to theinjection location. An example of a suitable needle-free jet nozzlearrangement is disclosed in U.S. Pat. No. 6,309,371.

At a proximal side of the fluid chamber 22, opposite from the needle 24,is a plunger 28 that preferably seals the medicament in the fluidchamber 22. A container wall 30 preferably comprises a tubular portion,preferably closed at a distal end and open at a proximal end, to definethe fluid chamber 22. Plunger 28 is slideably received in the tubularportion. The container 18 is configured such that when the plunger 28 isdisplaced in a distal direction, the volume of the fluid chamber 22 isdecreased, forcing the medicament out therefrom and through theinjection port 25 and the bore of needle 24.

At the distal end of the fluid chamber 22 is a needle hub portion 32 towhich the needle is mounted. A container flange 34 extends radially,preferably from the proximal end of the container wall 30.

In the preferred embodiment, the container 18 has a container body 36that includes the flange 34, wall 30, and hub portion 32 of unitaryconstruction. A preferred material for the container body 36 is glass,but other materials can be used in other embodiments. For example, asuitable prefilled syringe is the BD Hypak™, which is available invarious sizes and volumes and is sold prefilled with medicament. Theglass of the syringe body is adhered to the needle. Typical medicamentsand medicament categories include epinephrine, atropine, sumatriptan,antibiotics, antidepressants, and anticoagulants.

In some embodiments, the injector includes a container cushionconfigured for providing additional support to the container within thehousing, such as disclosed in International Application No.PCT/US2006/0002429, now WO 2006/079064. The container cushion 38 ispreferably made of an elastomeric material or other resilient material.A flange of the container cushion 38 extends radially and is disposedand serves as an interface between the distal side of the containersupport member 16 and the container flange 34. Elevated portions, suchas nubs, preferably extend proximately from the cushion flange and areconfigured and dimensioned to abut the container flange 34. A sleeveportion of the container cushion 38 extends axially around the interiorof the container support 16. The container cushion 38 is preferablyreceived in the interior of the container support 16 and receives thecontainer body 36, preferably fitting snugly therein.

Referring to FIGS. 1 and 2, trigger mechanism 52 is preferably alsohoused within outer housing 12. The trigger mechanism 52 includes aninner member, such as an inner housing 54, that can be attached to theouter housing 12, such as by snaps, an adhesive, a weld, or other knownattachment. Trigger protrusions 56 extend inwardly from the proximal endof the inner housing 54 and are normally resiliently biased outwardly.Trigger protrusions 56 are received in a recess 58 of firing ram 60 inblocking association therewith. The trigger protrusions 56 preventdistal movement of the ram 60 prior to the firing of the injector 10upon actuation of the trigger mechanism 52. The rain 60 is urged towardsthe distal end of the injector 10 by an energy source, which preferablyis a compression spring 62, although other suitable energy sources canalternative be used such as elastomer or compressed-gas springs, or gasgenerators. A preferred type of compression spring is a coil spring.

A trigger member of the trigger mechanism 52, such as a latch housing64, is provided exterior to the inner housing 54 to retain the triggerprotrusions 56 in the blocking association in the recess 58 to preventpremature firing of the injector 10. The latch housing 64 is slideableinside the outer housing 12 with respect to the inner housing 54,preferably in an axial direction, and the latch housing 64 preferablysurrounds the inner housing 54.

The distal end of the outer housing 12 preferably includes a needleguard 66 that is moveable with respect to the outer housing 12. Theneedle guard 66 is shown in FIG. 2 in a protecting position, in whichthe needle 24 is disposed within the guard 66. The needle guard 66 isretractable, preferably into the outer housing 12, in a proximaldirection to an injecting position, in which the needle tip 26 and anend portion of the needle 24 is exposed for insertion into a patient. Inthe preferred embodiment, the proximal movement of the guard issubstantially prevented at the injecting position. In embodiments wherethe container does not include a needle, the injection port and thedistal end of the fluid chamber can be exposed upon retraction of theneedle guard to the injecting position.

The needle guard 66 is associated with the latch housing 64 such thatwhen the guard 66 is displaced distally it slides the latch housing 64also in a distal direction to release the trigger protrusions 56 fromthe recess 58. Preferably, the latch housing 64 has a latching portionthat abuts the inner housing 54 in an association to bias and maintainthe trigger protrusions 56 positioned in the blocking association withthe ram 60 prior to the firing of the injector 10. When the latchhousing 64 is slid proximately by the retracting of the guard 66 to theinjecting position, the latching portion slides beyond the portion ofinner housing 54 that it contacts, allowing the trigger protrusions 56to move radially outwardly from the recess 58 and therefore from theblocking association. When this happens, i.e., when the triggermechanism 52 is actuated, the spring 62 biases the ram 60 againstplunger 28 to fire the injector 10. Latch housing 64 preferably definestrigger openings 70 adjacent to the latching portions, which areconfigured to receive a portion of the inner housing 54, such as thesurface disposed radially outwardly from the trigger protrusions 56.

The guard 66 is preferably resiliently biased distally towards theprotecting position by compression coil spring 72, or other biasingmember. Also, the needle guard 66 has an axial opening 74 to allow theneedle 24 pass therethrough, and which may be sized according to thetype of injector desired. In embodiments of the injector that do notinclude a needle, the axial opening can be sized to allow the distal endof the fluid chamber and injection port to pass therethrough. Theconstruction of the embodiment of FIG. 2 allows a user to push thedistal end of the injector 10 against the patient's skin, pushing theneedle 24 into the skin at an injection location, substantially at thesame speed as the injector is pushed. Once the needle 24 is fullyinserted to an insertion point at a penetration depth, the triggermechanism 52 fires the injection of medicament into an injectionlocation.

Other embodiments can incorporate alternative trigger mechanisms foractuating firing of the injector. For example, the injector can includea button or other suitable depressible member on the outer housing that,upon depression thereof, actuates firing of the injector.

Preferably, the injecting position of the guard 66 is such that apredetermined length of the end of needle 24 is exposed from the guard66. In some embodiments, such as where the opening 74 is of asufficiently large diameter, the skin of the patient maybe allowed toextend into the opening 74 when the device 10 is pressed there against,and a needle or injection port that does not protrude beyond the distalend of the guard 66 can be used. Some embodiments have a guard with adistal, skin-contacting surface that is discontinuous. In mostembodiments where the injector includes a needle, the distance by whichthe needle tip extends past the distal end of the guard will be fairlyclose to the depth of the insertion of the needle.

In the preferred embodiment, such as for subcutaneous injection, theguard 66 is configured to allow insertion of the needle to a penetrationdepth in the skin that is up to about 5 mm below the skin surface. Morepreferably, the penetration depth is less than about 4 mm, and in oneembodiment is less than about 3 mm. Preferably, the insertion depth isat least about 0.5 mm and more preferably at least about 1 mm. Inanother embodiment, the distance by which the needle extends past theguard 66 or the distal surface of the guard 66 that contacts the skin isup to about 5 mm, more preferably up to about 4 mm, and in oneembodiment up to about 3 mm. Preferably, extension distance is at leastabout 0.5 mm, more preferably at least about 1 mm, and most preferablyat least about 2 mm. In a preferred embodiment, tip 26 extends by adistance of around 2.5 mm beyond the portion of the guard 66 thatcontacts the skin in the injecting position.

In another embodiment, such as for intramuscular injection, the injectoris configured to allow the needle to be inserted into the patient to apenetration depth in the skin, or alternatively beyond the distalsurface of the guard, by a distance of up to about 15 mm. In oneembodiment, this distance is about between 10 mm and 14 mm. In anembodiment for jet injection of epinephrine for instance, a preferredpenetration depth or distance beyond the guard is between about 12 mmand 13.5 mm, and most preferably around 12.7 mm. Jet injection with thislength needle improves the distribution of the medicament in the patienttissue compared to non-jet injection. Other exposed needle lengths canbe selected for jet injection to different depths below the skin, with apreferred overall penetration length of between about 0.5 nun and about20 mm. In these embodiments, the needle guard is preferably configuredfor retracting from a protecting position, preferably covering theentire needle, to an injecting position, in which the desired length ofthe end of the needle is exposed. In alternative embodiments, the needletip stops behind or proximal to the guard, and penetrates the skin thatis pushed into the guard.

In sonic embodiments, the energy source, which is preferably spring 62,and the container, which is preferably prefilled syringe 18, areconfigured to jet inject the medicament into the patient to an injectionsite. The spring 62 applies a force on the plunger 28 that is preferablysufficient to elevate the pressure within the fluid chamber 22 to alevel high enough to eject the medicament from the needle 24 as a jet.Jet injection is to be understood as an injection with sufficientvelocity and force to drive the medicament to locations remote from theneedle tip 26 or injection port 25. The jet injector embodiments delivera jet injection, the medicament is jet injected distally or in otherdirections, such as generally radially by the elevated pressure jet,which beneficially improves the distribution of the medicament after theinjection and keeps a large bolus from forming that can detrimentallyforce the medicament to leak hack out of the patient around the needleor through the hole left behind by the needle after it is removed. Inalternative autoinjector embodiments that use needles, the injectionpressures are relatively very low, and the medicament exits the needletip inside the patient and is typically deposited locally around theneedle in a bolus,

Preferably, in embodiments where needles are used, the needles arebetween 26 and 28 gage, and are most preferably around 27 gage, butalternatively other needle gages can be used where the other componentsare cooperatively configured to produce the desired injection.Preferably, the components of the injector 10 are configured to jetinject the medicament to a subterraneous injection site.

Preferred injection rates are below about 0.75 mL/sec., more preferablybelow about 0.6 mL/sec., and preferably at least about 0.2 mL/sec., morepreferably at least about 0.3 mL/sec, and most preferably at least about0.4 mL/sec. Preferably, the injection of the entire amount of medicamentis completed in less than about 4 seconds, more preferably in less thanabout 3 seconds, and most preferably in less than about 2.5 seconds.Preferably, the medicament injection takes at least about 1 second, andinure preferably at least 1.5 seconds, and most preferably at leastabout 1.75 seconds. A preferred embodiment injects the medicament atabout 0.5 mL/sec., completing the injection of 1 mL in about 2 seconds.Other alternative injection rates, injection volumes, and injectionstimes can also be used.

The entire amount of medicament contained and injected from fluidchamber of the container is preferably between about 0.02 mL and 4 mL,and preferably less than about 3 mL, and in the preferred embodiment isaround 1 mL. Larger volumes may also be selected depending on theparticular medicament and dosage required. Preferably, the container 18shown in FIG. 1 is assembled into the remaining parts of the injector 10already containing the desired amount of medicament. In a preferredembodiment, the container 18 contains about 1 mL of medicament.

As shown in the preferred embodiment of FIG. 1, the injector 10 includesa volume-control mechanism 90 configured to select the fraction ofmedicament in the fluid chamber 22 that is to be injected, orcorrespondingly the dosage volume to be injected. The volume-controlmechanism of this embodiment includes the ram 60, a cap 82, and astopping member 100.

The ram 60, as previously described, preferably has a threaded portion61 and is configured for rotating about its longitudinal axis 110 topermit the option of injecting less than all of the medicament. Stoppingmember 100 preferably includes a body portion 102, which can beconfigured as an internally threaded nut, and at least one lateral wing,and preferably two lateral wings 104 extending laterally, and preferablyon opposing sides of the body portion 102. The body portion 102 ispreferably in threaded association with the ram 60 and is longitudinallymoveable therealong. Each of the lateral wings 104 is preferablydisposed and slideable within respective tracks 106 that extendlongitudinally. Tracks 106 are preferably associated with or are definedin the outer housing 12, and are positioned in the embodiment shown onopposite lateral sides of the outer housing 12. Each of the tracks 106preferably has a proximal end 107 and a distal end 108, which define atrack length therebetween. Upon rotation of the ram 60, tracks 106prevent rotation of the lateral wings 104 about the longitudinal axis110. Consequently, the position of the body portion 102 moves or isadjusted proximally or distally longitudinally along the threadedportion 61 of the ram 60, the lateral wings 104 sliding in the tracks106 therewith. In the preferred embodiment, the distal end 108 of thetrack 106 acts as to blocking member and prevents distal movement of thestopping member 100, and enlarged portion 101 of the ram 60 preventsproximal movement thereof, but other structures can alternatively beused for this purpose.

By rotating the ram 60, the stopping member 100 is positioned to limitthe throw of the ram 60 when the injector 10 is fired, allowing theselection of volume of medicament to be injected from the fluid chamber22. Upon actuation of the spring 62 by the trigger mechanism 52, the ram60 is biased distally against the plunger 28, thus displacing plunger 28in a distal direction to force medicament out of the fluid chamber 22.Movement of the ram 60 distally against the plunger 28, and thus thevolume of medicament that is injected from the fluid chamber 22 (i.e.,the injection volume), is limited by the lateral wings 104 of thestopping member 100. For example, the ram 60 can only move distally uponactuation of the spring 62 until the lateral wings 104 are stopped bythe distal ends 108 of the tracks 106. At that point, further movementof the ram 60 in the distal direction is prevented. The position of thestopping member 100 along the ram 60 thus effectively controls theinjection volume of medicament injected from the fluid chamber 22.

The operable member for rotating the ram 60 about the longitudinal axis110 to adjust the longitudinal position of the stopping member 100 ispreferably cap 82 that is preferably removeably engageable with the ram60. The cap 82 preferably includes an engagement portion 83 configuredfor mating receipt within a receiving portion 84 of the ram 60. In thisconfiguration, twisting or rotation of the cap 82 while the engagementportion 83 is received in the receiving portion 84 results in rotationof the ram 60 about the longitudinal axis 110. By manipulating the cap82, the position of the stopping member 100 can be adjusted proximatelyor distally along the ram 60 to select the fraction of medicament thatis desired to be injected from the fluid chamber 22. The engagement andreceiving portions 83,84 are preferably non-circular to prevent orrestrict axial rotation therebetween.

In the preferred embodiment, for example, the length of the tracks 106is substantially equal to the length between the distal end 109 of thefluid chamber 22 and the distal end of the plunger 28. Thus, when cap 82is twisted to position the stopping member 100 in its most proximalposition along the ram 60 (i.e., with the lateral wings 104 disposedagainst the proximal ends 107 of the tracks 106), actuation of thespring 62 causes the rain 60 to move distally against the plunger 28 asthe lateral wings 104 slide along the entire length of track 106 beforeabutting the distal ends 108 of the tracks, and the plunger 28correspondingly is moved distally through the fluid chamber 22 to thedistal end 109 thereof, injecting the entire volume of medicamenttherefrom.

If the cap 82 is twisted to position the stopping member 100 moredistally along the ram 60, then the injection volume will only be afraction of the entire volume of medicament in the fluid chamber 22because upon actuation, the lateral wings 104 will slide along thetracks 106 and abut the distal ends 108 thereof to prevent the ram 60from biasing the plunger 28 completely to the distal end 109 of thefluid chamber 22. As such, the entire volume of the medicament in thefluid chamber 22 is not injected. One of ordinary skill iii the artwould understand that the cap 82 can be twisted to adjust the positionof the stopping member 100 relative to the ram 60 to select theappropriate injection volume of medicament that is desired to beinjected.

Alternative embodiments can be provided with different throw andadjustment ranges to limit the range of adjustability to less than from100% to 0% of the total volume of contained medicament. In oneembodiment, the upper limit of volume fraction is less than 100%, e.g.,about 90% or about 80%, and the lower limit is more than 0%, e.g., about10%, 30%, or 50%. Additionally, other embodiments of the injector caninclude alternative mechanisms that are configured to limit thethrow/adjustment ranges or the volume of medicament ejected from theinjector.

Preferably, the outer housing 12 includes a window portion 110 adjacentthe tracks 106 and along the length thereof, as shown in the preferredembodiment of FIG. 4. The window portion 110 is preferably made of ahard and durable, yet substantially transparent, material to allow theposition of the lateral wings 104 of stopping member 100 to be visibletherethrough. More preferably, the window portion 110 includes indicia112 along and adjacent the length of the tracks that corresponds to theinjection volume to be injected from the fluid chamber 22. For example,the indicia can include marking intervals between 0% to 100% (the 0%marking disposed adjacent the distal end 108 of the track and the 100%marking disposed adjacent the proximal end 107 of the track) such thatadjusting the position of the stopping member 100 so that the lateralwings 104 are substantially aligned with a 75% marking indicates thatthe injection volume will be 75% of the entire volume of medicamentcontained in the fluid chamber 22.

One of ordinary skill the art would understand that other such indiciaor marking schemes can be used as desired. For example, indicia can beincluded on the housing adjacent the window rather than directly on thewindow, or the indicia can correspond to absolute values of injectionvolumes rather than percentages of the entire volume of medicament inthe fluid chamber.

The preferred embodiment of the injector 10 shown in FIG. 1 alsoincludes a bearing disposed between the spring 62 and the rain 60. Thebearing is preferably an annular bushing 68, such as a nylon washer. Thebushing 68 is configured for preventing or substantially reducingfriction between the spring 62 and the ram 60 as the ram is rotatedabout the longitudinal axis 110, while still transferring biasing energyfrom the spring 62 to the ram 60 upon actuation of the spring.

While the preferred embodiments disclosed herein have been described interms of a single-use injector (i.e., where a single injection volume ofmedicament is injected from a container prior to replacing the usedcontainer with a new container), one of ordinary skill in the art wouldunderstand that in other embodiments of the present invention, multipleinjection volumes can be injected from the same container. For example,a first injection volume of 80% of the entire volume of medicament inthe fluid chamber may be injected, followed by a subsequent injection ofa second injection volume of the same or different fraction of theremaining volume of medicament in the fluid chamber.

The preferred embodiment is a single-use injector, being configured toprevent a user from reloading and reusing the injector. As such, theembodiment of FIG. 1 does not have a way of resetting the injector tofire again, and preferably cannot be reloaded to with another medicamentcontainer without substantial disassembly or breaking of the injector.An alternative embodiment, however, is a reusable injector that can bereset, such as by reloading the firing mechanism and reloading themedicament.

The content of International Application No. PCT/US2006/0002429, now WO2006/079064, is hereby expressly incorporated herein by referencethereto. The term “about,” as used herein, should generally beunderstood to refer to both the corresponding number and a range ofnumbers. Moreover, all numerical ranges herein should be understood toinclude each whole integer within the range.

While illustrative embodiments of the invention are disclosed herein, itwill be appreciated that numerous modifications and other embodimentsmay be devised by those skilled in the art. For example, the featuresfor the various embodiments can be used in other embodiments. Therefore,it will be understood that the appended claims are intended to cover allsuch modifications and embodiments that come within the spirit and scopeof the present invention.

1-17. (canceled)
 18. An injection device for injecting medicament in apatient comprising: a housing configured to house one of a plurality offluid chambers, each one of the plurality of fluid chambers having adifferent fluid chamber volume; a fluid chamber having a first volume ofa medicament; an injection conduit associated with the fluid chamber fordefining a fluid pathway from the fluid chamber to the patient; a firingmechanism associated with the fluid chamber and configured to expel themedicament from the fluid chamber through the injection conduit; and avolume control mechanism configured to be adjusted to select a fractionof the first volume of medicament from the fluid chamber that isinjected from the injection conduit when the firing mechanism isactuated.
 19. The injection device of claim 18, wherein the firingmechanism comprises: a ram positioned along a longitudinal axis of theinjector and configured to be biased toward a distal end of the injectorwhen the firing mechanism is actuated to expel the medicament; a triggerhaving protrusions that are resiliently biased outwardly relative to thelongitudinal axis of the injector, the trigger protrusions being in ablocking association with the ram in a protecting position in which theinjection conduit is disposed within a retractable guard; a slidablelatch housing retaining the trigger protrusions in blocking associationwith the ram in the protecting position and allowing the triggerprotrusions to move radially outwardly from the blocking associationwith ram in an injection position in which a tip of the injectionconduit is exposed for injection of the medicament at an injectionlocation;
 20. The injection device of claim 19, wherein the retractableguard is positioned at a distal end of the injector, the retractableguard being moveable between the protecting position and the injectionposition, wherein the retractable guard is associated with the latchhousing such that when the retractable guard is retracted from theprotecting position to the injection position it causes the latchhousing to slide proximately to allow the trigger protrusions to moveradially outwardly from the blocking association with the ram, therebyallowing the ram to actuate the fluid chamber.
 21. The injection deviceof claim 20, wherein: the ram is threaded; and the volume controlmechanism comprises: a stopping member in threaded association with thethreaded ram, wherein the threaded ram is rotatable with respect to thestopping member for selectively positioning the stopping memberlongitudinally along the ram to select the fraction of the medicament,and a blocking portion positioned to block distal movement of thestopping member associated with the ram when the firing mechanism isactuated to expel the medicament.
 22. The injection device of claim 21,wherein the stopping member comprising at least one lateral extensionthat protrudes laterally from the ram to a position longitudinallyaligned with the blocking portion.
 23. The injection device of claim 22,wherein the volume control mechanism defines a track that extendsgenerally longitudinally, the lateral extension being slidably receivedtherein, wherein the lateral member is configured to prevent rotation ofthe stopping member about the longitudinal axis when the ram is rotatedthereabout for repositioning the stopping member longitudinally alongthe ram.
 24. The injection device of claim 23, wherein housing definesthe track, and wherein the track has a distal end that comprises theblocking member.
 25. The injection device of claim 24, wherein thehousing includes: a window adjacent the length of the track such thatthe longitudinal position of the stopping member within the injector isvisible through the window; and indicia adjacent the window fordetermining the selected injection volume of the first volume to beinjected.
 26. The injection device of claim 21, wherein the volumecontrol mechanism further comprises an exterior user-control associatedwith the ram for rotating the ram about a longitudinal axis to select aninjection volume by selectively repositioning the stopping memberlongitudinally on the ram.
 27. The injection device of claim 26, whereinthe exterior user-control is configured for disengagement from the ramwhen the firing mechanism is actuated to expel the medicament.
 28. Theinjection device of claim 27, wherein the exterior user-control includesa cap mounted on the housing and having a rotational coupling thatextends into the housing and is rotationally fixed with the ram forrotating the ram by rotating the cap, wherein the rotational coupling isconfigured to disengage from the ram when the ram is driven away fromthe coupling upon activation of the firing mechanism.
 29. The injectiondevice of claim 19, wherein the firing mechanism further comprises anenergy source activatable for expelling the medicament, and theinjection conduit is configured for jet injecting the medicament. 30.The injection device of claim 29, wherein the conduit comprises aninjection-assisting needle.
 31. The injection device of claim 29,further comprising a bearing member disposed between the energy sourceand the ram and configured for reducing friction therebetween when theram is rotated.
 32. The injection device of claim 21, wherein the firingmechanism further comprises an energy source activatable for expellingthe medicament, and the ram is operably associated with the energysource such that the ram is biased by the energy source when the firingmechanism is activated.
 33. The injection device of claim 18, whereinthe container is a prefilled syringe, and the injector further comprisesan injection-assisting needle disposed in fluid communication with thefluid chamber, the needle having an injecting tip configured forpiercing the patient's skin at the injection location.
 34. The injectiondevice of claim 18, further comprising retractable guard disposed at adistal end of the injector and movable from an extended position to aninjecting position for activating the firing mechanism.